Research on optimization of double insulating glass spacing design scheme.
The high latitudes of the northern hemisphere are cold areas in winter, with extremely low temperatures and large indoor and outdoor temperature differences. To meet the living requirements of residents in winter, good insulation design of buildings is required. Among them, the thermal insulation performance of windows is a very important link in the thermal insulation performance of buildings.
Building doors and windows are the weakest parts of the building envelope in terms of thermal insulation performance. Its long-term energy consumption accounts for about 50% of the long-term energy consumption of the entire building. Therefore, improving the thermal insulation performance of doors and windows is an important step in reducing the long-term energy consumption of the building.
The thermal insulation performance of windows not only significantly affects the heating energy consumption of the building, but also has a significant impact on the indoor thermal environment, comfort, and indoor hygiene. If the insulation quality of windows is poor, the heat loss through heat transfer through the windows and the heat loss through air penetration through the window gaps will increase significantly, which will lead to a significant increase in heating energy consumption.
The currently widely used insulating glass is a new building material that is heat-insulating, sound-insulating, beautiful, and practical, and can reduce the weight of the building. This project aims to study the design scheme of double insulating glass spacing and strive to arrive at an optimized spacing scheme that can achieve a higher level of thermal insulation performance, and conduct experimental verification to provide certain guidance for the future window thermal insulation design of buildings in high latitudes in the northern hemisphere. In addition, the double-layer insulating glass produced by LIJIANG Glass's fully automatic insulating glass production line has a long service life, good thermal insulation effect, and is economical and practical.
1. The experimental plan
The thermal insulation performance of glass windows is directly reflected by the heat transfer coefficient K value. The lower the heat transfer coefficient, the less heat dissipation and the better the thermal insulation performance of the window. Therefore, this experiment mainly explores the glass spacing combination that minimizes the heat transfer coefficient under the existing technical conditions. By formulating the gradient combination of spacing, experiment to measure the heat transfer coefficient, draw the image of the change of the spacing combination and the heat transfer coefficient, and study the relationship between the spacing combination and the heat transfer coefficient based on the image, and propose the optimal solution that satisfies the optimal thermal insulation performance. Excellent spacing combination to complete the research. After exploring the combination, we will study the orientation of δ1 and δ2, that is, the placement direction during the glass installation process, and study the impact of different orientations on the thermal insulation performance of the window. After the final spacing combination is determined, the optimal orientation is further explored to further improve the thermal insulation performance of the windows and provide a basis for the installation of windows during the building construction process. According to previous experimental data, when the distance between the double glass is less than 10 mm, the relationship between the distance and the thermal resistance is almost linear; when the distance between the double glass is 10 mm ~ 30 mm, the relationship between the distance and the thermal resistance is a curve; when the distance exceeds at 30 mm, due to the combined effect of convection and radiation heat exchange, the thermal resistance of the air layer increases very slowly.
The design should appropriately determine the spacing of the glass based on the needs of thermal resistance and the economic scale of the frame material. Generally, it should not be less than 9 mm. Currently, the two-glass windows widely used on the market include plastic windows, wooden windows, aluminum alloy windows, and aluminum-plastic composite windows. The heat transfer coefficients are all between 2.4 and 2.5 W·m-2·K-1, and those with slightly lower quality are as high as 2.8 W·m-2·K-1, coupled with errors in heating and other conditions in winter, the living environment of ordinary residents certainly does not have the excellent conditions of the laboratory, and this coefficient will be higher in practice. We also visited student dormitories on campus and measured the indoor temperatures. In some places, the indoor temperature was only 15°C. It is not difficult to find that most heat is lost through the windows, causing greater pressure on heating and a greater waste of resources. When the window glass changes from single glass to double glass or triple glass, the thermal insulation performance of the glass will be significantly improved. This is not the thermal resistance of the glass, but the air layer between the glass is the main reason for the increase in thermal resistance because the heat transfer coefficient of still air is lower than that of any material.
Therefore, with the improvement of the development level of glass window technology, to better improve the thermal insulation performance of doors and windows, triple glass windows can be made. According to the relationship between the thermal resistance of the airtight air layer and the thickness of the air layer, the net spacing thickness that meets the better thermal insulation performance is studied, and the orientation of different spacings of the glass is studied to complete the research of this project.
2. The experimental process and results
Based on the influence of airflow, glass thickness, and other factors on the heat transfer coefficient of glass windows, equal spacing can achieve the best thermal insulation effect. If one of the two spacings is too large and the other is too small, according to the changing trend of the K value of the double-glass glass, the too-large spacing takes on most of the thermal insulation tasks. However, when the glass spacing is too large, the heat transfer coefficient will not be significantly reduced, and the heat transfer coefficient will not be significantly reduced. The width will become smaller and smaller, so too large a spacing can only be a waste, and too small a spacing is too sensitive to the thermal insulation effect. A slight increase in the spacing will cause a substantial reduction in the heat transfer coefficient, so it is not suitable to use Too small a spacing, too large or too small a spacing will eventually lead to deterioration of thermal insulation performance, so it is assumed that equal spacing minimizes the window heat transfer coefficient.
According to the research, the three glass windows currently widely used in the market are 3 mm + 3 mm, 6 mm + 6 mm, 9 mm + 9 mm, and 12 mm + 12 mm. Glass windows with smaller spacing are mainly used for smaller openings in auxiliary rooms such as bathrooms, while glass windows with larger spacing are mainly used for larger openings in main rooms with high thermal insulation requirements such as living rooms and bedrooms.
At the same time, the author conducted research in Finland or Norway, a high-latitude country in the northern hemisphere, and actually participated in the experiment of measuring the heat transfer coefficient, and obtained some experimental data. The common three-glass windows of these specifications are 12 mm + 12 mm. The thermal conductivity is the lowest. The main material is plastic windows. The thermal conductivity is 1. 7～1. 8 W·m-2·K-1. Three-glass wooden windows: 1.7～1. 8W·m-2·K-1. Aluminum Plastic composite triple glass: 2.0～2. 1 W·m-2·K-1.
Commonly used in the market are three-glass windows with equal spacing, but what about unequal spacing? Because the heat transfer coefficient decreases linearly when the glass spacing is before 10 mm, so excluding the possible combination of 3 mm, it cannot play the role of still air. The advantage of low thermal conductivity. At the same time, considering that too thin triple glass windows will also make the thermal conductivity close to the double glass, several combinations were drawn up based on 12 mm + 12 mm: 6 mm + 18 mm, 9 mm + 15 mm, and these two spacing combinations were conducted experimented. The experiment is basically consistent with the hypothesis. The combined heat transfer coefficient of 6 mm + 18 mm spacing is 2. 2 W·m-2·K-1, and the combined heat transfer coefficient of 9 mm + 15 mm is 2. 0W·m-2·K-1. Comparing this with the heat transfer coefficient of triple-glazed windows of 12 mm + 12 mm specifications, it is not difficult to see that the heat transfer coefficient of the triple-glazed windows of 12 mm + 12 mm combination is the lowest among these combinations, so it can be concluded that the current optimal The spacing combination of is the equal spacing combination. Imagine a wide spacing combination, such as 15 mm + 15 mm, but based on current thermal resistance needs, technology level, and economical size of the frame, the total spacing combination is 24 mm, 15 mm + 15 mm such a spacing combination is even higher The spacing combination is not economical because it would lead to a sudden increase in the cost of window frame production at the current level of technology, so this possibility is ruled out.
3. The conclusion
Based on research, experiments, analysis, and data collection, it is concluded that triple glass windows with a spacing combination of 12 mm + 12 mm are currently the most economical and heat-insulating spacing combination. Such windows should be widely used in large openings in various buildings to replace two-pane windows or triple-pane windows with other spacing combinations whose heat transfer coefficient is much lower. For bathrooms, storage rooms, kitchens, corridors, and other auxiliary rooms that do not require high thermal insulation performance compared to main rooms such as living rooms and bedrooms, a spacing combination of 9 mm + 9 mm or lower can be used. Although they do not have 12 mm + 12 mm spacing insulation, the thermal insulation requirements of these rooms are not as high as those of the main rooms. This spacing can meet the thermal insulation requirements of these auxiliary rooms and is higher than the thermal insulation performance of two-glass windows, making it more economical.
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